Technical Abstract:
Salmonella is an important food bourn pathogen capable of infecting both humans and animals. One of the most effective treatments for Salmonella infections is beta-lactam antibiotics, particularly extended spectrum beta-lactams; however, Salmonella resistant to these antibiotics have been recovered from humans and animals. To investigate this further, isolates collected and analyzed by the animal arm of the National Antimicrobial Resistance Monitoring System (NARMS) were studied. While resistance appears to depend largely upon serotype and animal source, resistance to amoxicillin/clavulanic acid increase most rapidly between 1997 and 2005 with minor increases in chicken isolates and an apparent leveling off among cattle isolates. Resistance among swine isolates has remained below 3.5%for all years while resistance among turkey isolates rose above 11% for the 1st time in 2007. Resistance to ceftiofur patterns that observed for amoxicillin/clavulanic acid as described. Mechanisms of resistance are being investigated and among animal isolates appear to be mostly due to the cmy-2 AmpC beta-lactamase, whereas this and a variety of other beta-lactamases appear to be responsible for resistance in human isolates. These data suggest that resistance among animal isolates differs from that observed among human isolates.